1. Field of the Invention
The present invention relates to a wheel support bearing assembly for rotatably supporting a wheel relative to a vehicle body structure in automotive vehicles such as automobiles and also relates to an angular ball bearing for use in various applications.
2. Description of the Prior Art
For the wheel support bearing assembly, a dual row angular ball bearing is largely employed, in which dual rows of balls are rollingly interposed between outer and inner members at a predetermined contact angle. In such a dual row angular ball bearing, the balls of each row are retained by a respective ball retainer in circumferentially equidistantly spaced relation to each other and are prevented by the ball retainer from contacting with each other.
In wheel support bearing assemblies available in recent years, from the perspective of increasing the freedom of design choice of the automotive vehicles and the mileage and of facilitating the maintenance and reduction of the cost, the needs have arisen to further increase the lifetime and the rigidity of the wheel support bearing assembly, to manufacture the wheel support bearing assembly in a compact size and light-weight feature.
In an attempt to satisfy those needs, the Japanese Laid-open Patent Publication No. 2002-195254, for example, discloses a wheel support bearing assembly, in which one of the dual rows of balls, for example, an inboard row of balls, which is positioned remote from a vehicle wheel supported by the wheel support bearing assembly, makes no use of a ball retainer, i.e., represents a full complement ball bearing. The full complement ball bearing with no ball retainer employed is particularly advantageous in that the number of the balls can be increased, reducing a bearing load imposed on each of those balls. For this reason, the wheel support bearing assembly can have an increased lifetime and can also be manufactured in a compact size having a light-weight feature.
Although in the full complement ball bearing the number of the balls can be increased as compared with the bearing assembly utilizing the ball retainers, it has been well recognized that the neighboring balls contact with each other. Considering that during the operation of the bearing assembly the balls rotate in the same direction about their own center axes, the respective surfaces of the neighboring balls move in opposite directions at a contact point where such surfaces contact, with the consequence that a sliding contact or friction takes place at the contact point at a velocity that is twice the peripheral velocity of each ball. In other words, a so-called “ball-to-ball competition (ball-to-ball sliding friction)” occurs.
Once the ball-to-ball competition occurs, the frictional resistance increases. Also, in the full complement ball bearing, separation and collision of the balls repeat during the operation of the bearing assembly, which would lead to generation of rattling sounds and heat.
While the bearing assembly with the balls retained by the ball retainers is known to be advantageous in that the occurrence of the ball-to-ball competition and collision can be avoided, it is preferred that pillars in the ball retainers, that define a pocket between the neighboring pillars for accommodating the corresponding ball, may be as thin as possible in order for the number of the balls employable in the bearing assembly to be increased. The thinnest portion of the pillar needs to be aligned with the pitch circle of the row of the balls. However, to render each pillar to be thin is limited in view of the strength and manufacturing difficulty. By way of example, if each pillar is made too thin, the ball retainer is susceptible to damage at such a thin portion of the pillar and debris resulting therefrom will hamper a smooth rotation of the bearing.
The problems discussed above can be equally found in the standard angular ball bearing, particularly where the angular ball bearing is desired to be manufactured in a compact size with an increased load bearing capacity.